SUMMARYExperimental batches of hay were baled a t different moisture contents, and the microbial and biochemical changes studied by sequential sampling. The type of hay obtained could, in general, be related to the initial moisture content, and to the temperature subsequently attained. Good hays (about 16 yo moisture) heated little and contained a small but diverse microflora.Hays baled at about 25 oh moisture heated to about 45" and moulded, mainly with Aspergillusglaucus. Wet bales, with initial moisture contents of about $0 yo, became very hot (60°-650) and contained a large flora of thermophilic fungi, particularly Aspergillus fumigatus, Absidia spp., Mucor pusillus, Huinicola lanuginosa, and actinomycetes. During the initial heating period, which was correlated with a general rise in numbers of micro-organisms, particularly actinomycetes and bacteria, the acidity and volatile nitrogen increased. Later, when fungi and actinomycetes grew profusely, soluble sugars decreased rapidly and the pH value rose to 7-0 or above. Stacks of wet and dry hays were compared with bales made from the same hays. The wet stack developed a core of brown acid hay, containing many sporeforming bacteria but few fungi, surrounded by a layer of mouldy hay.

SUMMARY:Estimates of numbers of micro-organisms occurring in three differently manured soils, made by a direct-counting and plating technique, were compared. No correlation was found between the two methods and reasons for the large discrepancy between them are discussed. Contradictory information of the effect of external factors on soil micro-organisms can be given by the two different methods of counting.Estimates of the total numbers of bacteria in soil obtained by a direct-counting technique devised by Jones & Mollison (1948) are of the order of several thousands of millions/g. soil, while estimates by conventional plating methods are in tens of millionslg., even on the least selective media so far used. The same authors found a difference of the same kind between the quantity of fungal mycelium in soil as estimated by a direct count of number of pieces/g. as compared with colony plate counts, although in this comparison the former count is only 2-6 times greater than the latter.The effect of external factors such as soil moisture and temperature on the various groups of soil microflora has been investigated by several workers and, while certain correlations have been found, the results have been conflicting. The estimations of numbers of organisms were mainly based on plate counts. The present investigation was undertaken to compare direct counts with plate counts over a period of time, to determine how these varied with soil moisture and temperature and to show whether these two counting methods did, in their different ways, give the same sort of information about the soil population. The soils of three differently manured plots were sampled at intervals (Fig. 1) over the greater part of a year, and determinations made of the moisture content of these samples and of their bacterial, fungal and actinomycetal populations, by plating and a direct-counting technique. 'METHODSSoil sampZing. The soil samples were taken from three of the classical plots of Broadbalk field, which has grown wheat continuously for just over 100 years and whose plots have had different manurial treatments over that period.Plot 2 (farmyard manure), plot 3 (no manure) and plot 7 (complete minerals + ammonium sulphate) were sampled at intervals between January and December. Soil was collected by an auger to a depth of 4 in. in 12 areas on each plot; these were bulked and passed through a 3 mm. sieve. From these sieved samples the necessary amounts of soil were taken for the determination

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SUI\IMARYIn moist hay allowed to self-heat aerobically in Dewax flasks, the pattern of temperature change with time was affected considerably by the type of hay and duration of storage, but there was a relationship between water content and maximum temperature reached, Below 29 yo water content there was little heating or antigen production; in the critical range of 29-34 yo water content, different lots of hay self-heated to different temperatures between 33 and 55" and varied widely in their content of farmer's lung hay antigen complex (FLH), the wetter hays usually producing the more antigen; all samples with 40% water heated to c. 6.5' and produced FLH antigen, associated with the presence of Thermopolysporu polyspora. Progressively less antigen, especially in the lower regions of the flasks, was produced as water content increased from 47 to 68 yo. Moist barley and oat grain also self-heated and produced FLH antigen, usually only in the middle of the grain mass, where T . polysporu was most abundant; the drier upper layers and the lower regions where excess water accumulated were free from the antigen. INTRODUCTIONThe self-heating of baled hay has been studied in relation to the microbial and biochemical changes during moulding and to the development of antigens of immunological significance in farmer's lung disease (Gregory et al. 1964). Pepys et al. (1963) attributed the presence of these antigens (FLH complex) to the growth of the thermophilic actinomycetes Thermopolyspora polysporu and Micromonospora vulgaris.The first laboratory experiments on self-heating of hay were made by Miehe (1907) who used a central wire container filled with hay surrounded by similar containers insulated with cotton-wool. Dewar flasks were used first by Hildebrandt Our experiments in Dewar flasks began as studies on the effects of water and aeration on the self-heating process, in attempts to reach high temperatures. Hay very rich in FLH antigen was produced so the effect of water on antigen production A weighed quantity of chopped hay (usually 500g.) was moistened in a polythene bucket to the required water content, thoroughly mixed by hand and then transferred to a 4 1. Dewar flask. A 1 1. and a 10 1. Dewar flask were also occasionally used, and in one experiment a barrel lagged with glass fibre sheet was filled with 15 kg. hay that had been moistened and mixed on a concrete floor. Water content is given as percentage wet weight, and weights of hay given all refer to the weight before adding water.In experiments with barley (14% water content), 2.5 kg. grain was used and water added to give a content of near 40 %, but the water was not all absorbed and some accumulated at the bottom of the 4 1. Dewar flask. In one experiment, as also in the experiment with oats (12 yo water content), the grain was left to stand with the added water with occasional mixing, for 5 hr, before all the water was taken up. A plug of cotton-wool about 2 cm. thick was placed on the surface of the hay or grain and one or two extra similar layers p...

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Spore germination and hyphal growth from spores of the vesicular–arbuscular endophyte Glomus mosseae have been studied under different oxygen and carbon dioxide tensions. Spores failed to germinate at low oxygen tension. This effect was reversible. However, mycelial growth from spores not preincubated in air was irreversibly damaged. The mycelial growth from preincubated spores was affected by oxygen tension. Between 21 and 3% oxygen, growth decreased slightly. Below 3% oxygen it decreased sharply. Again this effect was reversible. A tension of 5% carbon dioxide had no effect on spore germination, but reduced hyphal growth consistently at all oxygen tensions. This effect persisted when spores were subsequently returned to air.

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